Evolution of the Hβ + [O III] and [OII] luminosity functions and the [O II] star formation history of the universe up to z ~ 5 from HiZELS

Abstract

We investigate the evolution of the Hβ + [O III] and [O II] luminosity functions from z ~ 0.8 to ~5 in four redshift slices per emission line using data from the High-z Emission Line Survey (HiZELS). This is the first time that the Hβ + [O III] and [O II] luminosity functions have been studied at these redshifts in a self-consistent analysis. This is also the largest sample of [O II] and Hβ + [O III] emitters (3475 and 3298 emitters, respectively) in this redshift range, with large comoving volumes ~1 × 106 Mpc-3 in two independent volumes (COSMOS and UDS), greatly reducing the effects of cosmic variance. The emitters were selected by a combination of photometric redshift and colour-colour selections, as well as spectroscopic follow-up, including recent spectroscopic observations using DEIMOS and MOSFIRE on the Keck Telescopes and FMOS on Subaru. We find a strong increase in L* and a decrease in ϕ* for both Hβ + [O III] and [O II] emitters. We derive the [O II] star formation history of the Universe since z ~ 5 and find that the cosmic star formation rate density (SFRD) rises from z ~ 5 to ~3 and then drops towards z ~ 0. We also find that our star formation history is able to reproduce the evolution of the stellar mass density up to z ~ 5 based only on a single tracer of star formation. When comparing the Hβ + [O III] SFRDs to the [OII] and Hα SFRD measurements in the literature, we find that there is a remarkable agreement, suggesting that the Hβ + [O III] sample is dominated by star-forming galaxies at high-z rather than AGNs.